Preheat the oven to 400F.
Heat the butter in a frying pan, add the bacon and cook until the edges are lightly browned.
Add the chopped onion and continue cooked until the onion bits are translucent.
Throw in the spinach. Sprinkle with salt and pepper. Stir and cook for about a minute.
Pour in the cream. Cook, stirring, just until the cream is bubbly.
Arrange the bread slices on a tray and toast in the hot oven for about four minutes.
Take the bread out of the oven. Spread the bacon-spinach mixture on each slice of bread. Top with grated cheese.
Return the tray back into the oven and toast the bread just until the mozzarella melts.
You may garnish the creamed bacon and spinach toast with snipped parsley before serving.